1. Field
One embodiment of the invention relates to a method of forming a housing used for electronic apparatuses such as portable computers, in particular, a method of ejecting a molded article serving as a base of a housing from a metal mold by using a plurality of ejector pins. Further, the present invention relates to a housing that is molded by filling a molten material between a pair of metal molds.
2. Description of the Related Art
Recently, electronic apparatuses such as portable computers having a housing made of magnesium alloy are known. Housings made of magnesium alloy have advantages that reduction in weight and thickness can be more easily achieved while stiffness is secured than in housings made of synthetic resin or aluminum alloy.
Housings made of magnesium alloy are mass-produced by using molding devices. The molding device has a pair of metal molds which are detachably engaged. A molding space is formed between the metal molds. Molten magnesium alloy is filled into the molding space and hardened therein, and thereby a molded article having a shape corresponding to a housing is obtained. The molded article is ejected from the molds, and then subjected to chemical treatment, primer application, painting, and clear coating, etc.
When the molded article is ejected from the molds, a method of using a plurality of ejector pins is conventionally adopted. The ejector pins push up the molded article from one of the metal molds, and are vertically movably attached to one of the metal molds. The ejector pins are scattered to cover a wide range of the molded article such that they can push up the molded article without inclining the article.
On the other hand, a basic thickness of housings of magnesium alloy is empirically set to 0.8 mm or less. Therefore, the molded articles serving as a base of the housings are formed to have a very small thickness. Thus, if conventional ejector pins are adopted, the thin molded article may yield to a pushing force applied from the ejector pins when the molded article is ejected from the molds.
If the molded article is deformed, its surface serving as the exterior surface is warped. This warp causes diffusion of light after clear coating is applied to the molded article. Therefore, warp is particularly conspicuous in housings obtained by applying clear coating to molded articles. This causes deterioration in appearance of the housings.